The aim of the project is to build a low-cost, invisible laser circuit to protect our house from thieves or trespassers. A laser pointer torch, which is easily available in the market, can be used to operate this device. A laser torch powered by 3V power supply is used for generating a laser beam. A combination of plain mirrors is used to direct the laser beam around the house to form a net. The laser beam is directed to finally fall on an LDR that forms part of the receiver unit. Any interruption of the beam by a thief/trespasser will result into energisation of the alarm

i like to add on.....i.e call the owner.....when an intruder cuts the laser beam.....i checked for many ways to connect a call.... finally read an article...that uses just relay to activate a call.....will that logic works???....please help me with your suggestions

....doesn't sound to be a very good security system. Since you are intending to use a single beam with a LDR, someone could simply shine a flashlight on your LDR and walk about the house at whim, without the LDR ever noticing a broken beam. I think you may want to make a more robust system before you deal with communicating a break-in.

Something like a GSM module can text you, call you, snap a picture and MMS it to you, whatever you'd like...

i would like to make a call.....as i said earlier according to an article on anti theft alarm..
it has an IR sensor,delay circuit, oscillation control circuit and mobile.....sensor detects...oscillation ckt comprises of a monostable multi connected to a relay....which is then connected to mobile.....will this work?? please give your suggestions....

i would like to make a call.....as i said earlier according to an article on anti theft alarm..
it has an IR sensor,delay circuit, oscillation control circuit and mobile.....sensor detects...oscillation ckt comprises of a monostable multi connected to a relay....which is then connected to mobile.....will this work?? please give your suggestions....

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I gave you suggestions, even how to do it if you insist on using a flawed design.

You asked if it would work. If poor performance is your goal, then yes, it will work wonderfully, though I'm sure the wonder will come in whether or not it works.